The McMurdo Dry Valleys are a group of mostly snow-free desert valleys along the coast of Victoria Land, Antarctica, located east of the East Antarctic Ice Sheet and west of McMurdo Sound and the Ross Sea. These valleys are well-known for being the coldest and driest desert on Earth, as well as the largest area without ice in Antarctica. Because of this, the valleys are an important area for scientific studies in Antarctica. The unique climate of the Dry Valleys is caused by their position between the Transantarctic Mountains and strong, cold winds called katabatic winds that remove snow and moisture from the area. Mountains around the valleys stop ice from nearby glaciers from moving into the region. The area's rock formations are mainly made of granite and gneiss, and glacial deposits cover the bedrock, with loose gravel on the ground. Although the valleys are one of the driest places on Earth, some people have reported seeing rain in the area.
The region includes several features, such as Lake Vida, a salty lake, and the Onyx River, a stream of melted water and Antarctica's longest river. No living things have been found in the frozen ground here, but bacteria that live inside rocks and use sunlight to grow have been discovered in the slightly wetter parts of the rocks. Bacteria that do not need oxygen and use iron and sulfur for energy have also been found under the Taylor Glacier.
The valleys are part of the McMurdo Valleys Antarctic Specially Managed Area (ASMA-2).
Climate
The Dry Valleys are one of the most extreme places on Earth and are called a cold desert. They cover about 4,500 square kilometers (1,700 square miles), which is 0.03% of Antarctica’s land area. This region is the largest ice-free area in Antarctica.
The very low amount of rain and snow in the Dry Valleys is caused by the Transantarctic Mountains, which create a "snow shadow" effect. These mountains are up to 3,000 meters (9,800 feet) high. Because of this, much of the valley floors are exposed and covered with loose gravel. Ice wedge patterns can be seen in this gravel.
The unique conditions in the Dry Valleys are partly due to katabatic winds. These winds form when cold, heavy air moves downhill because of gravity. These dry winds quickly remove snow and cause very little snow to melt into the ground. During summer, this process can happen in just a few hours.
Another important factor is the very low amount of precipitation. Over 100 years of records show that the area gets about 100 millimeters (4 inches) of precipitation each year, mostly as snow. This leads to very dry air in the region.
Even though there is little snow or surface ice, the Dry Valleys have more than 6,000 lakes and ponds.
For a few weeks each summer, temperatures rise enough to cause glaciers to melt. This creates small streams of fresh water that flow into lakes at the bottom of the valleys. These lakes do not drain into the sea, so they become very salty.
The highest and lowest air temperatures recorded in the McMurdo Dry Valleys (MDVs) were 12.0°C (53.6°F) at Taylor Glacier and −65.7°C (−86.3°F) at Lake Vida, respectively. The average yearly air temperature on valley floors ranges from −14.7°C (5.5°F) at Lake Bonney to −29.6°C (−21.3°F) at Lake Vida. In Taylor Valley, which has eight stations, the valley bottom temperatures range from −14.7°C (5.5°F) to −23.0°C (−9.4°F). Temperatures at four glacier stations range from −15.1°C (4.8°F) to −19.4°C (−2.9°F).
At higher elevations, temperatures range from −20.7°C (−5.3°F) to −25.2°C (−13.4°F). When comparing the average yearly temperatures of the valleys using valley bottom stations, from warmest to coldest, they are: Miers Valley (−16.5°C or 2.3°F), Taylor Valley (−18.5°C or −1.3°F), Wright Valley (−19.8°C or −3.6°F), and Victoria Valley (−26.8°C or −16.2°F).
Geology
The McMurdo Oasis is surrounded by the coastline of south Victoria Land and the Polar Plateau. The Taylor and Wright Valleys are important ice-free valleys located within the Transantarctic Mountains. These "dry valleys" include hummocky moraines, with frozen lakes, saline ponds, sand dunes, and meltwater streams. Basement rocks include the Late Precambrian or Early Palaeozoic Skelton Group metamorphic rocks, primarily the Asgard Formation, which is a medium-high-grade marble and calc schist. The Palaeozoic Granite Harbour intrusives include granitoid plutons and dykes, which intruded into the metasedimentary Skelton Group in the Late Cambrian – Early Ordovician during the Ross orogeny. The basement complex is overlain by the Jurassic Beacon Supergroup, which is itself intruded by Ferrar Dolerite sheets and sills. The McMurdo Volcanic Group intrudes, or is interbedded with, the Taylor and Wright Valleys' moraines as basaltic cinder cones and lava flows. These basalts have ages between 2.1 and 4.4 Ma. The Dry Valley Drilling Project (1971–75) determined the Pleistocene layer within the Taylor Valley was between 137 and 275 m thick, and composed of interbedded sandstones, pebble conglomerates, and laminated silty mudstones. This Pleistocene layer disconformably overlies Pliocene and Miocene diamictites.
Research
Since the Dry Valleys were discovered in the early 1900s and research stations like McMurdo Station (United States) and Scott Base (New Zealand) were built on nearby Ross Island in the 1950s, scientists have studied the region extensively. The valleys' extremely dry and cold climate was soon recognized as a strong example of Mars' environment, and researchers have used the area to test scientific methods since NASA's Viking Program in the 1970s.
In 1985, the first weather station was placed at Lake Hoare. In 1992, Taylor Valley, the southernmost of the three major Dry Valleys, was chosen as a National Science Foundation Long Term Ecological Research (LTER) site. This allowed scientists to study ecological changes over many years. As of August 2025, there are 26 real-time weather stations, stream monitors, and observation platforms, and 1,028 scientific papers linked to the LTER program.
In 2013, Irish and American scientists visited University Valley to study microbes and test a Mars-like drill in the driest parts of the valleys, which are most similar to Mars. They found no living organisms in the frozen soil, making University Valley the first place on Earth where humans searched and found no active life.
Scientists have also studied ice-covered lakes and streams in the valleys. These lakes remain frozen due to cold temperatures, but some ice is lost through sublimation (ice turning directly into vapor), and water from melting glaciers flows into them during seasons.
Microbial mats have been found in streams, lakes, wetlands, and ice in the region. These mats are unique because strong winds constantly remove surface material.
Bacteria that live inside rocks, protected from the dry air, have been found in the Dry Valleys. These bacteria survive in the moist centers of rocks, and nutrients come from summer glacier meltwater.
Anaerobic bacteria that use iron and sulfur for energy live under Taylor Glacier in freezing temperatures.
It was once believed that algae caused the red color of ice at Blood Falls, but scientists now know the color comes from high levels of iron oxide.
In 2014, scientists from Auckland University of Technology used drones in the McMurdo Dry Valleys to create maps showing plant locations. In 2015, the New Zealand Antarctic Research Institute funded the team to develop drone technology. Over several summers, the team made highly detailed 3D maps, which are now used as reference points.
Part of the Dry Valleys was declared an environmentally protected area in 2004.
Major geographic features
From north to south, the three main valleys are located in the region.
West of Victoria Valley, the following valleys extend from north to south:
From west to east, the area stretching south from Balham Valley includes:
West of Taylor Valley, the following valleys are found:
Further south, between the Royal Society Range in the west and the west coast of McMurdo Sound near the lobe of Koettlitz Glacier, the following valleys extend from north to south:
Some lakes in the Dry Valleys are among the world's most saline lakes, with salinity levels higher than those of Lake Assal or the Dead Sea. The saltiest lake is the small Don Juan Pond.